There has existed the need for a high speed punching assembly to be used with the higher speed turret punch presses. High operating speeds and the increased use of standard tooling have created problems for prior punching assemblies, particularly when they are used to notch or nibble a workpiece. In a notching or nibbling operation in which a large area needs to be removed, a punch of a smaller size than the area to be removed can be used to nibble the material out in small bites. This creates a substantial lateral pressure on the punch since the punch is being used on only one or two sides. In the prior punching assemblies, the punch holder travels up and down in the press turret during this side loading, causing galling, seizing and bell-mouthing of the turret. It is therefore a general object to reduce this kind of wear and the expensive rework or replacement of the turret by limiting wear to the internal parts of the punching assembly.
In addition, the lubrication of previous punching assemblies has been a hit or miss proposition. This has contributed to premature damage and replacement of parts. Moreover, prior tools have had a tendency to overheat. It is therefore an object to provide a more effective means for lubricating and cooling the punching assembly, particularly the operating end of the punch.
The high speed steel from which the punch is made, while excellent in high temperature and abrasion resistance, is quite fragile and susceptible to chipping and spalling at its cutting edge. It is therefore an objective to support the punch at the working end in two dimensions, namely, by supporting it against both lateral and rotary movement.
Thus, in prior punching assemblies, wear was excessive and too much time was required to remove and replace the punch in from the punch assembly. The general objectives of the invention are to reduce wear, provide finished parts of better quality, i.e., flatter sheets, less burrs, longer punch life, quicker punch changing with more reliable and trouble free operation.
Punch devices have been previously proposed that include an external housing or sleeve within which the punch itself slides during operation. It is also known to provide a removable stripper plate surrounding the punch tip as shown for example in U.S. Pat. No. 4,248,111. These prior devices have certain shortcomings. Stripper plates are time-consuming to remove and replace. They also require a special tool for the manipulation of several retaining members used for securing the stripper in place. It is therefore one object to provide a way of more quickly and easily removing and replacing the stripper plate and punch including a self-locking provision that automatically secures the stripper plate in place. Moreover, prior punches of the type having a stripper could be used only as a push-type punch and were not suited for use with a push-pull ram, i.e., one in which the punch is pushed downwardly into engagement with the work and is also pulled back on the return stroke.
In view of these and other deficiencies of the prior art, the present invention has the following more specific objectives and advantages:
(a) The provision of an improved punching assembly having a means for more quickly and easily removing and replacing the punch and stripper plate;
(b) The provision of a feature for automatically locking the stripper plate in place on any one of several preset angular positions about the punch axis assembly;
(c) Provision for more effectively lubricating internal parts;
(d) Provision for the above-noted features in a push-pull style punch suited for use in a push-pull type punch press or press brake;
(e) A provision that enables the stripper plate to guide the punch both laterally and about its axis for improving alignment and stability especially when notching and nibbling;
(f) A provision for cooling the operating end of the punch by causing air to flow over it;
(g) A provision enabling the stripper plate to be removed with a single quick movement of the hand and to be ejected automatically with a pop-out action;
(h) The provision of a single retaining member for holding the stripper plate securely in place so that by shifting the retaining member the punch and stripper plate can be removed and replaced in about 30 seconds;
(i) Provision for enabling the punch and stripper plate to be removed for replacement while keeping the rest of the punch assembly intact;
(j) Provision for producing an audible signal when the punch has been released and can be removed; and
(k) Provision for making a length adjustment to compensate for punch length changes and the amount of punch penetration into the die.
These and other more detailed specific objects of the invention will be apparent in view of the following description setting forth but a few of the various ways in which the present invention can be accomplished in view of the accompanying description which illustrates the invention by way of example.